Automotive vehicles utilize transmissions to transmit power from the engine to the drive wheels or tires. The transmission provides an interface between the engine and the drive wheels such that the driver can vary the speed of the vehicle over a wide range.
Automotive vehicles at the present time utilize fixed ratio transmissions. These transmissions have a set of gears that provide a few fixed and discrete speed ratios between the input from the engine and the output to the tires. Engine rpm (revolutions per minute) varies over a wide range for each speed ratio. Because the engine must operate over a wide range of speeds, its overall efficiency is reduced.
Continuously variable transmissions offer a way to boost engine efficiency. Unlike fixed ratio transmissions, continuously variable transmissions offer a wide range of speed ratios between the input from the engine and the output to the tires. This allows the engine to operate over a narrow range of optimum rpm, wherein the engine can be increased. By varying the speed ratio, the engine rpm can be maintained in its optimum range, even for a variety of driving conditions, thereby improving fuel efficiency.
Prior art continuously variable transmissions utilize a belt to couple two sheaves together. One sheave is an input sheave while the other is an output sheave. The sheaves can vary their effective diameter, so as to control the speed ratio. The problem with belt driven transmissions is that the belts cannot handle the engine power produced by large engines.